the third level of law-enforcement - police are known to be the 5-0, security gaurds and bouncers (club security) constitute the 4-0 - whereas the 3-0 represents school teachers or other citizens who are on the look out for people up to no good.

pronounced "three-oh"

Ay dawg, lets cut class.
No dice, the 3-0 are out in force patrolin today, we'll get busted fo sho.

derived from the roman numerals xxx, meaning both 30 and porn. came around in the 21st century when members of the GPK needed code words to get past their parents. also makes it more comfortable to talk about porn.

While Steve's mom was in the room...

Alex: Hey, dudes, i found some sick ass 30 last night.

Dan: Aww no way. i got grounded from the computer cuz my parents found out about my 30